Lubricant



Pat ented Feb. 17, 1948 LUBRICANT Lawson W. Mixon, Hammond, Ind.assignor to Standard Oil Company, Chicago, 111., a corporation ofIndiana No Drawing. Application August 29, 1944, Serial No. 551,717

7 Claims. (c1. 25.2-33.6)

The present invention relates to improvements in lubricants and moreparticularly to lubricants containing an adjunct which imparts to thelubricants varnish inhibiting properties.

More particularly the invention relates to lubricating oil compositionsadapted for use in ,internal combustion engines of the spark ignitionand compression ignition types wherein under operation conditionscorrosion, piston ring stick, ing, cylinder wear and varnish formationare substantially reduced.

Straight petroleum lubricants are effective within certain definedlimits of engine operating conditions but when these limits areexceeded, such lubricants frequently fail to give the desiredperformance required of them, Since in modern engines designed to giveincreased performance, these limits are frequently exceeded, the use ofstraight hydrocarbon oils as lubricants produce undesirable conditionswithin the engine, thus varnish and carbon formation becomes excessiveand corrosion of improved hard metal alloy type bearings is encountered.

It is ,an object of this invention to provide a lubricant which isresistant to the formation of varnish. It is another object of thisinvention to provide a hydrocarbon oil composition adapt- -ed for use ininternal combustion engines and which is resistant to the formation ofsludge, acidity and varnish and which is non-corrosive to bearingmetals, particularly bearing metals of the hard metal alloy type. Otherobjects and advantages of this invention will become ap-,

parent as the description thereof proceeds.

I have discovered that the foregoing objects can be attained by addingto a lubricant composition containing a lubricating oil such as, forexample, an animal, vegetable, marine, or a hydrocarbon oil such as amineral or petroleum oil, a metallic salt of an organicpolythiocarbonate in small but sufiicient quantities to inhibit varnishand/or sludge formation in such lubricant. Generally from about 0.05% toabout Ira-(Lam in which x is an element selected from the groupconsisting of oxygen and sulfur. R is an organic group such as an alkyl,aryl, alkaryl, aralkyl, alicyclic or heterocyclic radical, and Mrepresents a metal such as, for example, lithium, sodium, potassium,magnesium, calcium, strontium, barium, copper, aluminum, chromium, tin,lead, iron, cobalt, nickel, titanium, tungsten, vanadium, and zinc. Theorganic group may contain inorganic substituents such as oxygen, sulfurand phosphorus, Particularly efiective for the herein-described purposeare the metal salts of terpene polythiocarbonate and the metal salts ofkeryl polythiocarbonates. The term "keryl polythiocarbonate" denotes asubstituted polythiocarbonate in which the hydrocarbon constituent is apetroleum fraction having distillation characteristics corresponding tothat of a kerosene fraction.

,The metal salts of the organic polythiocarbonates can be prepared byreacting an alcoholic solution of a hydrocarbon mercaptan and causticsuch as KOH with carbon disulfide. The alkali metal organicpolythiocarbonate can then be treated with a polyvalent salt to obtainany desired metal salt of the organic polythiocarbonate. The preparationof these compounds is exemplifled by the following examples'which aregiven by way of illustration only and are not intended as limiting thescope of the invention. The zinc salt of terpene trithiocarbonate wasprepared in the following manner: 108.5 grams of terpene mercaptan and42 grams of KOH was dissolved in 500 cc. of ethyl alcohol. To thisalcohol solution was added 48 grams of carbon disulfide and the mixturewas stirred for about 15 minutes at a temperature of about 80 F. Uponcompletion of this reaction grams of zinc chloride dissolved in 100 cc.of water was added to the mixture withstirring. The zinc salt of theterpene trithiocarbonate was separated from the reaction mass as areddish yellow oil by hexane extraction,

The zinc salt of keryl tri'thiocarbonate was prepared in the followingmanner: 108 grams of keryl mercaptan was dissolved in 300 cc. of ethylalcohol. To this alcohol solution was added grams of carbon disuliideand the mixture was stirred for about 15 minutes at about F. At the endof this reaction a slight excess of zinc chloride dissolvedin water wasadded to the mixture with stirring. The zinc salt of the keryltrithiocarbonate was separated from the reaction mass as a reddishyellow oil by hexane extraction.

The metal salts of the organic polythiocarbonates of the typeherein-described are particuhydrocarbons such as suliurized mineraloils,

sulfurized terpenes, substituted amines such as, for example, polyaminopolyaryl methanes such as aminomethyl-aminodiphenyl methane,tetramethybd'iamino-diphenyi methane, diimethyl amino) dina'phthylmethane and derivatives 01 the same.

The eiiectiveness oi the metallic salts of or- 4 game polythiocarbonatesin inhibiting varnish formation in internal combustion engines is 11-lustrated by the following data. These data were obtained by subjecting0113 containing the addifail-rust agents, extreme pressure agents andthe While I have described my invention with re!- erence to specificembodiments thereof, it is to be understood that the same are givenmerely by way of illustration and are not intended to limit the scope ofthe herein-described-invention except insofar as the same are defined bythe appended claims.

I claim:

1. A normally liquid lubricant composition comprising a major proportionof a hydrocarbon oil and from about 0.0b% to about 10% of a zinc organotrithiocarbonate oi the group consisting of a zinc alkyltrithlocarbonate and a zinc alicyclic trithiocarbonate.

2. A normally liquid lubricant composition resistant to the formation ofproducts of oxidative deterioration oi the type of varnish and sludge,

tives to accelerated engine tests made in the standard six cylinderspark ignition internal combustion engines operating for 60 hours at 35B. H. I. and 3000 R. P. M. with an oil sump temperature of 285 F. At theend of the test period the engines are dismantled. inspected and givenvisual ratings. In this visual rating system a rating 0! 10 means thatthe engine had substantially the appearance or the engine at the startof the test while a rating of 1 indicates that the engine aiter'the testshowed very extensive deposits of varnish and sludge. Engines havingappearances between these extremes are given intermediate rating values.An engine lubricated with 'good conventional motor oil for a 60 hourperiod usually merits a visual rating of about 5. The data presentedherein were obtained by subjecting the following oils to the foregoingtests:

Oil A.-,98.75% acid treated SAE-30 M. C. motor oil, 0.75% KOHneutralized reaction product of Past and isobutylene polymer, 0.25%suliurized mineral oil, 025% suliurized terpene.

Oil B.'Oll A+0.5% zinc terpenyl trithiocarbonate.

Oil O.-Qil A+0.5% zinc keryi trithiocarbonate.

The above data demonstrate the improvement in the overall and varnishrating due to the presence of the metallic soap oi the organicpolythiocarbonate. I

The present invention also contemplates the addition 0! other additivesto lubricant compositions such es, lo: example, antioxidants. pour pointdepressor-s, V. I. improvers, oiliness agents,

comprising a major proportion of a hydrocarbon oil normally susceptibleto oxidative deterioration and in combination therewith from about 0.05per cent to about 10 per cent of a zinc salt of an organictrithiocarbonate selected from the class consisting of an alkyltrithiocarbonate and an alicyclic trithiocarbonate and an additiveexhibiting detergency properties, the latter being used in small butsuiilcient quantities to inhibit the deposition or varnish and sludge onengine parts.

3. A normally liquid lubricant composition as described in claim 2 inwhich the additive exhibiting detergency properties is the neutralizedreaction product of a phosphorus sulfide and a hydrocarbon.

4. A normally liquid lubricant composition comprising a major proportionof a hydrocarbon oil and from about 0.05% to about 10% of a zinc salt ofan alkyl trithiocarbonate.

5. A normally liquid lubricant composition comprising a major proportionof a hydrocarbon oil and irom about 0.05% to about 10% of a zinc salt ofan alicyclic trithiocarbonate.

6. A normally liquid lubricant composition containing a major proportionoi a hydrocarbon oil REFERENCES CITED The following references are ofrecord in the file of this patent:

. UNITED STATES PATENTS Number Name Date 2,365,011 Rosen Dec. 12, 19442,289,105 McNab July 14. 1942 2,197,835 Reii! Apr. 23. 1940 2,346,155Denison et al. Apr. 11, 1044

